Cannula with proximally mounted camera

ABSTRACT

A cannula system and method for accessing a blood mass in the brain. The system comprises a cannula with a camera mounted on the proximal end of the cannula with a view into the cannula lumen and the surgical field below the lumen. A prism, reflector or other suitable optical element is oriented between the camera and the lumen of the cannula to afford the camera a view into the cannula while minimizing obstruction of the lumen.

This application is a continuation of U.S. application Ser. No.15/895,277, filed Feb. 13, 2018, now U.S. Pat. No. 10,105,042, which isa continuation of U.S. application Ser. No. 15/576,536, filed Nov. 22,2017, which is the National Stage of International ApplicationPCT/US2017/047424 filed Aug. 17, 2017, which is a continuation-in-partof U.S. application Ser. No. 15/239,632, filed Aug. 17, 2016, whichclaims priority to U.S. Provisional Application 62/483,885 filed Apr.10, 2017.

FIELD OF THE INVENTIONS

The inventions described below relate to the field of minimally invasivebrain surgery.

BACKGROUND OF THE INVENTIONS

Stroke is a common cause of death and disabling neurologic disorder.Approximately 700,000 patients suffer from stroke in the United Statesevery year. Hemorrhagic stroke accounts for 20% of the annual strokepopulation. Hemorrhagic stroke is due to a rupture of a blood vessel inthe brain, causing bleeding into the brain tissue and resulting in ahematoma (a blood mass) in the brain. Prompt removal of the blood massis necessary to limit or prevent long-term brain injury.

Clear visualization and imaging of the blood mass and any surroundingsurgical field facilitates removal of the blood mass. Removal andvisualization can often be accomplished through a cannula and obturatorassembly, placed through a hole drilled in the skull near the site ofthe hematoma. The site of the hematoma can be accurately identifiedusing a CT scan.

To aid in placement of the cannula and obturator assembly precisely atthe hematoma, and also to aid in inserting the cannula through a routeleast likely to damage healthy brain tissue, neurosurgeons usesophisticated and costly stereotactic surgery systems orneuro-navigation systems. These systems depend on previously obtainedMRI or CT scans, which may be several hours old, and thus not perfectlyreflective of the shape and location of the blood mass at the time ofsurgery. In these systems, visual confirmation that the cannula distalend is properly positioned can be accomplished only after the obturatorhas been removed from the cannula. If the distal end has not beenaccurately placed, the obturator must be re-inserted, and the cannulaand obturator assembly must be manipulated, perhaps repeatedly, until,after removal of the obturator, the blood mass is visible.

A less sophisticated method, used before these expensiveneuro-navigation systems and stereotactic systems became standard andstill used where these systems are not available, involves largecraniotomies, exploration and direct visual search for a blood mass,extensive tissue dissection, and invasive instrumentation, allassociated with high mortality and morbidity.

SUMMARY

The devices and methods described below provide for improvedvisualization of the brain during minimally invasive surgery. The devicecomprises a cannula with a camera mounted on the proximal end of thecannula with a view into the cannula lumen and the tissue within andbelow the lumen. A prism, reflector or other suitable optical element isoriented between the camera and the lumen of the cannula to afford thecamera a view into the cannula while minimizing obstruction of thelumen.

The devices including the cannula with a camera mounted on the proximalend of the cannula with a view into the cannula lumen and the tissuewithin and below the lumen, and optionally a display to display imagesobtained by the camera, can be used with an obturator comprising a long,small cross-section shaft with a short, large diameter tip which istransparent or translucent. The prism, reflector or other suitableoptical element is oriented between the camera and the lumen of thecannula to afford the camera a view of the obturator tip whileminimizing obstruction of the lumen. The assembled cannula, camera andobturator can be inserted into the brain of a patient, with theobturator tip used to gently dissect brain tissue to make way for theassembly, as well as obturate (occlude) the distal opening of thecannula. The small cross-section obturator shaft is much smaller thanthe inner diameter of the cannula, affording a sizable annular orcircular space between the shaft and the cannula wall to provide goodvisibility (from the camera) of the proximal surface of the obturatortip. Lights, if necessary, may be provided in the cannula to illuminatethe distal end of the obturator tip and cannula or tissue near thedistal end of the cannula (lighting may instead be provided from asource outside the assembly, or from lights mounted on the proximal endof the cannula or any combination of the foregoing). Light reflected bytissue near the distal surface of the obturator tip passes through theobturator and out of the proximal surface of the obturator tip, so thata surgeon inserting or manipulating the assembly can easily see that theobturator tip is near brain tissue (which is white to gray) or blood(which is red to black).

The system, and the method of access it enables, may be used as anadjunct to neuro-navigation to help confirm successful navigation to ahematoma, especially where the goal of the surgery is removal of theblood mass through the cannula. The system and the method it enables maybe used to locate a blood mass, in lieu of a neuro-navigation system, insituations where the approximate location of the hematoma is known fromimaging, or in situations where the approximate location of the hematomamay be ascertained with smaller probes, or during emergent surgery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the head of a patient with an area requiring surgicalintervention.

FIG. 2 illustrates a cannula with a proximally mounted camera.

FIG. 3 is an exploded side view of a cannula with a proximally mountedcamera.

FIG. 4 is a top view of a cannula with a proximally mounted camera.

FIG. 5 is a close-up side view of a cannula light shield with the cameramovable on a track.

FIG. 6 is a close-up side view of the camera for a cannula with aproximally mounted camera.

FIG. 7 illustrates the insertion of an obturator and cannula with aproximally mounted camera into a tissue mass in the patient of FIG. 1.

FIG. 8 illustrates the use of a cannula with a proximally mounted camerato perform minimally invasive surgery on the patient of FIG. 1.

FIG. 9 illustrates an additional structure of the cannula which providesfor easy attachment and detachment of the camera to the cannula tube.

FIGS. 10 and 11 illustrate the camera and cannula system in which thecamera is fixed to the cannula tube, and the obturator is modified topass the camera even as it encroaches on the space over the lumen of thecannula tube.

FIG. 12 illustrates a patient with a blood mass in the brain thatnecessitates surgical intervention, with a cannula which has beeninserted into the brain, with the distal end of the cannula proximatethe blood mass and an obturator tip extending into the blood mass.

FIG. 13 illustrates a cannula, camera and obturator system.

FIG. 14 illustrates removal of the obturator while the camera assemblyremains fixed to the proximal end of the cannula.

FIGS. 15, 16 and 17 depict exemplary images obtained by the camera whileadvancing the system through the brain.

FIGS. 18 and 19 illustrate obturator tips, for use with the cannula,camera and obturator system of FIG. 12.

DETAILED DESCRIPTION OF THE INVENTIONS

FIG. 1 illustrates a patient 1 with a blood mass 2 in the brain 3 thatnecessitates surgical intervention. A cannula 4 has been inserted intothe brain, with the distal end of the cannula proximate the blood mass.A camera 5 is mounted on the proximal rim of the cannula, with a portionof the camera overhanging the rim of the cannula and disposed over thelumen of the cannula, and is operable to obtain video or still images ofthe blood mass or other tissue at the distal end of the cannula.

FIG. 2 illustrates the cannula 4 in detail. The cannula comprises acannula tube 6, with a distal end 6 d adapted for insertion into thebody of the patient, and the proximal end 6 p which remains outside thebody during use. A camera 5 is mounted on the proximal end 6 p of thecannula tube. A mounting structure 7 secured to the proximal end of thecannula. The camera, shown in more detail in the following figures, mayinclude or be fitted with a prism, a reflector or other mirror structureor optical element, overhanging the lumen 8 of the cannula tube. If thecamera is small compared to the cannula lumen, the camera may be usedwithout the prism or reflector, and may be oriented with its viewingaxis aligned along the long axis of the cannula. The light necessary toprovide good visualization of the blood mass, and obtain images of theblood mass, may be provided by light sources 9 (LED's or other lightsource) disposed at the distal end 6 d of the cannula tube, at orproximate the distal opening. The light sources may instead be disposedat the proximal end of the cannula tube and the light may be transmittedthrough the open lumen of the cannula, or may be transmitted throughoptical fibers 10, or, if the cannula is made of a transparent material,the light may be transmitted down the walls of the cannula tube to exitthe distal end of the cannula wall to illuminate the blood mass. Thering 11 of the mounting structure 7 serves as a shield to block lightfrom view from a proximal viewpoint, whether the light emanates directlyfrom proximally located lights, or passes through the cannula tube fromdistally located lights. In embodiments in which the light sources aredisposed on the proximal end of a transmissive cannula tube, the distalportion 6 d of the cannula tube may be shaped, molded, machined, treatedor otherwise configured to enable the emergence of light from cannulatube 6 to illuminate the surgical field. For example, the inner distalsurface and/or the outer distal surface may be sanded or frosted orcoated to enable emission of light through the surfaces. Where the lightsources are disposed toward the distal end of the cannula, the portionof the cannula holding the light sources, and the portion of the cannuladistal to the light sources may be optically transmissive to generatemore light for the surgical field, while the portion of the cannulaproximal to the light sources may be opaque. Cables for providing powerto the camera and light source, and carrying image data from the camerato a display, may be provided, or the device may be powered by batteriesdisposed on the device and image data can be transmitted wirelessly to adisplay.

FIG. 3 is an exploded side view of cannula 4 with the camera 5 disposedon the proximal rim of the cannula tube, with a prism or reflector 12overhanging the lumen 8 of the cannula. FIG. 4 illustrates a top view ofcannula 4 with a proximally mounted camera 5. FIG. 3 also shows the LEDs9 disposed on or near the distal end 6P of the cannula tube to emitlight into the surgical field (such as blood mass 2).

The camera may be mounted within the mounting structure so that theprism or reflector 12 may be removed from its overhanging position,either by sliding the camera radially, flipping the camera around apivot, or by removing the camera from the camera mounting structureentirely. FIG. 5 illustrates a sliding attachment of camera 5 to themounting structure 7 as well as movement of the camera from a standbyposition 13S to a use position 13A. With camera 5 in use position 13A,the prism/reflector 12 extends partially or fully into the cylindricalspace 14 defined by and extending from the lumen 8 and affords anunobstructed view of surgical site at the distal opening of the cannulatube, while providing minimal interference to small diameter surgicalinstruments using lumen 8 to perform surgery (for example, an aspiratoror a macerator). Any suitable technique for moveably attaching thecamera 5 to the light shield 7 may be used. For example, the camera maybe slidably attached on a track such as track 15, in which case thetrack 15 secures the camera 5 to the light shield and enables thecamera/prism assembly to move radially between a standby position 13S toa use position 13A and back again (that is, from a first position inwhich the prism extends into the lumen 8 or the cylindrical space 14defined by the lumen of the cannula tube, to a second position in whichthe prism resides outside of lumen 8 or the cylindrical space 14 definedby the lumen of the cannula tube). The camera may also be attached witha pivot at 16, so that it is rotatably attached to the tube, from afirst position in which the axis of the camera is perpendicular, orsubstantially perpendicular, to the long axis of the cannula tube to asecond position angled from the long axis so that the prism residesoutside the cylindrical space 14 defined by a virtual extension of thelumen of the cannula tube. The camera may also be releasably attached tothe mounting structure (i.e., it may be readily attached and detached byhand, without the use of tools, during a surgical procedure) with afriction fit or detent arrangement between the camera and a channel ofthe mounting structure, or other suitable releasable attachment means.

FIG. 6 is a close-up side view of the camera 5. The camera 5 comprisesthe prism or reflector 12, a lens or lenses 17 (which may include anachromatic lens or other doublet), the imaging device 18 and the controlsystem 19 (if provided in the camera component of the system). The lens17 may be part of an optical assembly that includes additional opticalcomponents. The imaging device 18 may be any suitable image sensor suchas a CCD sensor or CMOS sensor. The control system 19 may include acontroller, data processing components and transmitters such as acontroller and a transmitter to control the camera and transmit datafrom the camera (the data output system may be located off the device).Suitable cables or wireless transmitters may be used to connect thecamera to a display system and a power supply. The imaging sensor ischaracterized by an imaging plane, and the prism is aligned with theimaging plane to direct light directed parallel to the imaging planetoward the imaging plane. As illustrated, the imaging plane is parallelto the long axis of the cannula tube, and the prism/reflector isdisposed along a line perpendicular to the imaging plane, and isoriented to direct light from the surgical field at the distal end ofthe cannula tube onto the imaging plane.

In the illustrated embodiment, a central longitudinal axis 20L extendsconcentrically throughout the length of the tubular body. The imagingsensor has an imaging sensor axis (a primary viewing axis) 20S,extending at a perpendicular to the sensor surface and intersecting aradially facing surface of the prism. As illustrated, the centrallongitudinal axis and the imaging sensor axis intersect at about a 90°angle. In alternative configurations, the angle is within the range offrom about 70° and 110°, or within the range of from about 85° and 95°.The angle may be greater than or less than 90° depending upon thedesired configuration.

In any of the embodiments disclosed herein, a prism viewing axis 20P (asecondary viewing axis, which is the line of sight through the cannula,from the prism to the distal end of the cannula) intersects a distalsurface of the prism, and extends axially distally through the tubularbody toward target tissue. In some implementations the prism viewingaxis intersects the central longitudinal axis of the cannula at aboutthe distal end of the cannula, or within about 4 cm or 2 cm or less fromthe distal end of the cannula. The prism overhangs the cannula lumen byno more than about 25% of the inside diameter of the lumen, generally byno more than about 15% or 10% or less of the inside diameter of thelumen. For this reason, the secondary viewing axis typically resides atan angle to the central longitudinal axis. Depending on the type ofprism used, the prism viewing angle may be perpendicular to the distaloptical surface of the prism (for a reflective, right angle prism shownin the figures, in which the long surface is used as the roof, forexample), and the prism may be disposed over the cannula lumen such thatthe distal optical surface is tilted slightly, relative to thetransverse plane of the cannula, to aim the prism viewing axis at thedesired point, such as an intersection with the central longitudinalaxis of the cannula at the distal end of the cannula. For otherreflective and deflective prisms for which the viewing angle is notperpendicular to the distal optical surface, the distal optical surfacecan be angled, as appropriate, to aim the prism viewing axis at thedesired point such as an intersection with the central longitudinal axisof the cannula at the distal end of the cannula. Various forms of prismsmay be used, including a pentaprism, half pentaprism (a non-invertingand non-reverting prism which bends light 45° from the prism viewingaxis, so that the imaging sensor viewing axis may be disposed at about a45° angle to the prism viewing axis or the cannula longitudinal axis), aSchmidt prism (an inverting and reverting prism which bends light 45°from the prism viewing axis, so that the imaging sensor viewing axis maybe disposed at about a 45° angle to the prism viewing axis or thecannula longitudinal axis), Porro prisms (an inverting and revertingprism which displaces the light entering the prism to an offset butparallel path, so that the imaging sensor viewing axis may be parallelto but radially displaced from to the prism viewing axis or the cannulalongitudinal axis) or other prisms, or combinations or configurations ofprisms (and Amici/Penta prism combination, for example, or a right angleprism disposed with the long surface facing distally, so that the rightangle surfaces serve the reflecting surfaces to redirect the image alongan anti-parallel path to the prism viewing axis, optionally paired witha second right angle prism to redirect the image to a parallel butoffset path, or a Bauerfeind prism), operable to reflect or displacelight from the distal end of the cannula toward the imaging sensor.

In embodiments in which illumination is provided by lights disposed onthe distal end of the cannula tube, any resultant glare and reflectionsfrom the inner wall of the cannula tube can be minimized by providingbaffles on the interior wall of the tube. The baffles may compriseridges protruding slightly into the lumen, dispersed along the length ofthe tube. Preferably, the ridges are progressively spaced, such thatthey are more closely spaced toward the proximal end of the tube, andrelatively more widely spaced toward the distal end of tube. Severalsuch ridges are illustrated in FIG. 3, marked as item 21. The ridges maybe provided in any form, and may be integral to the cannula tube 6 (forexample, formed during molding) or may be glued or fused onto the innerwall of the tube, or they may comprise turns of a coil, or turns of abraid, inserted into the tube or fused into the inner wall of the tube,and the coil or braid can comprise power or data cables associated withthe distally located lights or distally located cameras or sensors.

As shown in FIGS. 7 and 8, a surgeon inserts the cannula 4 with anobturator 22 into the patient's brain until distal end 6 d of thecannula is sufficiently close to tissue 2 for surgery. The surgeon thenremoves the obturator 22 so that the cannula 4 can be used to provideaccess, illumination and visibility for the surgical field. The surgeonthen moves camera 5, shifting, rotating, or moving it, depending on theconstruction, from a standby position to place the prism over the lumen.If necessary, the surgeon orients the imaging system to obtain a view ofthe surgical field. With the camera in place, the surgeon operates thecamera to obtain an image of the surgical field. Image data from camera5 is transmitted to the display 23 to provide image or images 24 of thesurgical field obtained through lumen 8. The image may include stillimages (photographs) and video. After placement of the camera, thesurgeon may pass surgical instruments, or the distal end of surgicalinstruments, through the lumen of the cannula, while the portion of thecamera is disposed within the lumen 8 or the space 14 over the lumen.

FIG. 9 illustrates an additional structure of the cannula 4 whichprovides for easy attachment and detachment of the camera 5 to thecannula tube 6. The camera is fixed to the mounting structure 25, andthe mounting structure is releasably attachable to the cannula tube. Themounting structure comprises a ring, similar to mounting structure andring combination shown in the previous figures (items 7 and 11) withfirst locking element such as a groove 26 on the inside of the ring, andthe proximal end of the cannula tube includes a second, complementarylocking element such as a flange 27, sized and dimensioned to fit snuglyin the groove of the mounting structure. The mounting structure may besnapped onto the cannula, when desired, to position the camera on theproximal end of the cannula tube, with the prism overhanging the wall ofthe cannula tube and disposed over the lumen 8. The mounting structureis releasably attached, in that it may be readily attached and detachedby hand, without the use of tools, during a surgical procedure. Otherreleasable attachment means, including a friction fit between themounting structure and the outside or inside wall of the cannula tube,or a magnetic attachment (with paired magnets in the cannula tubeproximal end and in the mounting structure), or a snap fitting, or adetent arrangement between the mounting structure and the cannulaproximal end, or a threaded fitting (with complementary inside andoutside threads on the mounting structure and cannula proximal end, orvice-versa), or a bayonet mount, with complementary slots and pins onthe mounting structure and cannula proximal end, or vice-versa, may beused.

Also, FIG. 9 illustrates an alternative embodiment of the baffles shownin FIG. 3. In FIG. 9, the baffles comprise turns of a coil 28. Thebaffles may also comprise a braid. The coil or braid can also comprisethe electrical wires needed to carry power to the lights disposed on thedistal tip of the cannula tube, or a sensor disposed on the distal tipof the cannula tube, and can also comprise data cables needed totransmit data from any such distally mounted sensor to control ordisplay systems associated with the sensors.

FIGS. 10 and 11 illustrate the camera and cannula system in which thecamera 5 is fixed (i.e. not releasably attached) to the cannula tube 6,and the obturator 22 is modified to pass the camera even as itencroaches on the space over the lumen of the cannula tube. In FIG. 10,the obturator 22 is essentially isodiametric throughout its length, andhas a groove 29 extending along its length (the portion disposed withinthe cannula tube). The groove is sized and dimensioned to accommodatethe prism that overhangs the lumen of the cannula tube. With thisconstruction, the obturator can be inserted into the cannula tube, andthe assembled cannula and obturator can be pushed into the brain, whilethe cannula is in place, fixed to the cannula. In FIG. 10, the obturator22 comprises a large diameter distal portion 22 d, with an outerdiameter approximately the same as the inner diameter of the cannulatube, and a small diameter rod 30 that fits easily within the lumen ofthe cannula tube. The camera is supported on a pylon or post 31. Thepost holds the camera away from the proximal opening of the cannulatube, at a sufficient distance, compared to the length of the largediameter portion 22 d of the obturator, so that the obturator may betilted or bent in order to insert large diameter portion 22 d of theobturator into the lumen without the need to move the camera.

FIGS. 12 through 19 illustrate a cannula, camera and obturator systemusing a cannula and camera system similar to that illustrated in FIG.11, with a transmissive obturator tip which allows a surgeon to seetissue beneath the obturator tip while inserting the assembled cannulaand obturator into the brain.

FIG. 12 illustrates a patient 1 with a blood mass 2 in the brain 3 thatnecessitates surgical intervention, with a cannula 4 which has beeninserted into the brain, with the distal end of the cannula proximatethe blood mass. A camera 5 is mounted on the proximal rim of thecannula, with a portion of the camera overhanging the rim of the cannulaand disposed over the lumen of the cannula, and is operable to obtainvideo or still images of the distal end of the cannula lumen, which mayinclude images of an obturator tip in the cannula or images of a bloodmass, brain tissue, cerebro-spinal fluid (CSF) or other tissue at thedistal end of the cannula. As shown in both FIGS. 12 and 13, the cannulacomprises a cannula tube 6 with a camera 5 and one or more light sourcesand a mounting structure 7 secured to the proximal end of the cannula.The camera includes a prism, reflector or other mirror structure oroptical element, overhanging the lumen 8 of the cannula tube. The cameramay be permanently fixed to the proximal end of the cannula (meaningthat it cannot easily be removed intraoperatively, without tools ordestructive disassembly) or releasably attached to the proximal end ofthe cannula (meaning that it can be readily attached and detachedintraoperatively, without the need for special tools or destructivedisassembly). A portion of the camera assembly, such as the prism,reflector or mirror, extends into the cylindrical space 14 defined bythe lumen of the cannula tube and extending proximally beyond theproximal end of the cannula, and is spaced from the proximal end of thecannula, and extends only slightly into the cylindrical space 14 (by nomore than about 25% of the inside diameter of the lumen, preferably nomore than about 15% or 10% of the inside diameter of the lumen) so thatthe obturator tip, when sized and dimensioned relative to the proximalspacing of the camera assembly and the intrusion of the camera assemblycomponent into the cylindrical space 14, may be tilted to avoid theintruding camera assembly component and pushed into the proximal end ofthe cannula. The camera may include a simple focusing means, such as athumbscrew or slidable post 32, operable by hand to move the imagingsensor radially inwardly or outwardly to adjust the focus of the camerato different depths within the cannula or beyond the distal end of thecannula.

The light necessary to provide good visualization of the blood mass, andobtain images of the blood mass, may be provided by lights 9 (LED's orother light source, shown in FIG. 13) disposed at the distal end 6 d ofthe cannula tube, at or proximate the distal opening. The cannula itselfis preferably opaque, and non-reflective, or coated with ananti-reflective coating. The LED's may instead be disposed at theproximal end of the cannula tube and the light may be transmittedthrough optical fibers, or, if the cannula is made of a transparentmaterial, the light may be transmitted down the walls of the cannulatube to exit the distal end of the cannula wall to illuminate the bloodmass. The ring 11 of the mounting structure 7 may serve as a shield toblock light from view from a proximal viewpoint, whether the lightemanates directly from proximally located lights, or passes through thecannula tube (if transparent) from distally located lights. A prism,reflector or mirror 12 overhanging the lumen 8 of the cannula allows thecamera to view down the long axis of the cannula, if the camera is largesuch that it must be mounted with its viewing axis perpendicular to thelong axis of the cannula. In embodiments in which the light sources aredisposed on the proximal end of the cannula tube, the distal portion 6 dof the cannula tube may be shaped, molded, machined, treated orotherwise configured to enable the emergence of light from cannula tube6 to illuminate the surgical field. For example, inner distal surfaceand or outer distal surface may be sanded or frosted to enable emissionof light through the surfaces. Cables for providing power to the cameraand light source, and carrying image data from the camera to a display,may be provided, or the device may be powered by batteries disposed onthe device and image data can be transmitted wirelessly to a display.

FIG. 13 also illustrates the obturator 33. The obturator comprises theobturator tip 34, shaft 35, handle 36, and mounting structure 37. Theobturator tip is a solid structure with a conically convex distalsurface 34 d, a conically convex proximal surface 34 p, and an axiallyshort circumferential surface 34 c. The tip, in the region of thecircumferential surface, has an outer diameter (a transverse diameter,along a plane perpendicular to the long axis of the cannula, andcorresponding to the transverse cross sectional diameter of the cannula)that closely matches the inner diameter of the cannula, but allows easylongitudinal translation of the tip through the lumen of the cannula.The tip, configured as shown in FIG. 13, will act as a lens, such thatlight rays (represented by arrows 38) are refracted through the tip, andbent such that any “image” passing through the tip, when formed asillustrated, may be reversed. The tip may have a rectilinearlongitudinal cross section, with a central cylindrical portion anddistal and proximal conical portions, as illustrated, or a more roundedcross section. The shape illustrated in the Figures may be described asa dual-ended conical spheroid, but the tip may also be a sphere, aspheroid, a prolate spheroid (a football, rugby ball), and oblatespheroid, or an ovoid (egg-shaped). The distal taper preferably ends inan acutely pointed tip which is preferred for use in the brain, but mayterminate in a blunt or rounded tip. The distal surface and proximalsurface need not be symmetric about the longitudinal axis, or symmetricabout a transverse axis. For example, the distal surface may be pointed,with a rectilinear cross section, while the proximal surface is pointed,rounded, or flat.

The obturator tip is optically transmissive, not optically opaque, andmay be optically transparent or optically translucent. The transmittanceof the tip need only be adequate, in the visible spectrum, to pass thecolor of tissue in contact with the distal surface, given the brightnessof any illumination provided by the light sources, to provide enoughtransmitted light to the camera and/or eye of the surgeon to allow thecolor of tissue around the tip to be discerned from light transmittedthrough the proximal surface of the tip. The tip may be made of glass,silica, acrylic, polycarbonate, silicone, nylon, polyamides orcopolymers or any other material suitable for use in a medical device.The obturator tip surface may be polished or frosted. The obturator tipmay optionally comprise radiopaque substances (elements or compoundssuch as platinum particles, for example) to render the tip radiopaque,so that it appears distinctly under fluoroscopy during surgery. Theobturator tip may optionally comprise sensors such as pH sensors,impedance sensors, force sensors, glucose sensors, etc., to assist indetecting a blood mass or CSF and distinguishing them from surroundingbrain tissue.

The proximal surface of the tip, which tapers to a small diameter in theproximal direction, also provides for clearance of the tip when theobturator must be removed to make room for other devices. As shown onFIG. 14, the convex surface allows for clearance from the camera, with aslight tilt of the obturator shaft away from the longitudinal axis ofthe cannula, so that removal of the obturator is not blocked by theoverhanging prism of the camera assembly.

The shaft 35 may be a solid rod or a tube, with a small diameter, ortransverse cross section, compared to the cannula lumen, so that the tipproximal surface can be viewed from the cannula proximal end. Ifprovided as a tube, the lumen of the shaft may accommodate aneuro-navigation stylet or probe 39 with passive markers detectable bythe neuro-navigation system, useful for guidance of the assembly intothe brain. The rod 40 of the neuro-navigation stylet may be insertedinto the lumen of tubular shaft, as shown, so that the assembledcannula, obturator and stylet may be tracked by a neuro-navigationsystem, through tracking of the markers 41 on a frame 42 to aid inaccurate placement of the distal tip of the assembly. The shaft 35 mayalso accommodate a neuro starburst connection. The shaft need not becircular, and may have a square or oval cross section, so long as theshaft transverse cross section is small compared to the cannula innerdiameter so that the tip proximal surface can be viewed from the cannulaproximal end. The shaft may alternatively comprise a half-pipe, with anouter diameter closely matching the inner diameter of the cannula, withthe half-pipe arranged opposite the camera assembly, leaving a largeportion of the cannula lumen clear for visualization of the tip from theproximal end of the cannula.

The obturator mounting structure 37 includes a depending rim 43, with akeyway 44 (see FIG. 14) sized to friction fit over a strut 45 or otherstructure of the camera mount or cannula rim or other component. Anyother suitable mating means, such as a notch in the cannula and amatching rail in the mounting structure, or a depending pin or rim onthe mounting structure which fits into a hole or circumferential channelin the cannula, may be used. The mating means also preferably serves tolimit the longitudinal travel of the obturator relative to the cannula,such that when the mating means is secured to the cannula, the obturatordistal surface protrudes from the distal end of the cannula. The matingmeans, such as the keyway or notch, may also serve as a means forregistering the rotational position of the tip, should it be desirableto provide an index indicia on the tip, to assist a surgeon inidentifying the location of features discernable through the tip,relative to structures on the proximal end of the assembly.

The camera 5 comprises the prism 12, a lens or lenses 17 (which mayinclude an achromatic lens or other doublet), the imaging device 18 andthe control system 19 (if provided in the camera component of thesystem). The lens 17 may be part of an optical assembly that includesadditional optical components. (For example, a stenopeic aperture may bepositioned in the light path between the prism and the sensor,preferably between the prism and the lens. This may be accomplished bymounting a sheet or applying a mask to the proximal surface of theprism, containing an aperture having a diameter within the range of fromabout 1.0-2.0 mm and in one embodiment about 1.5 mm.) The imaging device18 may be any suitable image sensor such as a CCD sensor or CMOS sensor.The control system 19 may include a controller, data processingcomponents and transmitters such as a controller and a transmitter tocontrol the camera and transmit data from the camera (the data outputsystem may be located off the device). Suitable cables or wirelesstransmitters may be used to connect the camera to a display system and apower supply. The imaging sensor is characterized by an imaging plane,and the prism is aligned with the imaging plane to direct light raystraveling through the cannula lumen substantially in parallel or at anon-parallel angle to the imaging plane toward the imaging plane. Asillustrated, the imaging plane is parallel to the long axis of thecannula tube, and the prism disposed along a line perpendicular to theimaging plane, and oriented to direct light from the surgical field atthe distal end of the cannula tube onto the imaging plane. 46474849

FIG. 14 illustrates removal of the obturator while the camera assemblyremains fixed to the proximal end of the cannula. As shown in FIG. 14,the tapered proximal surface of the tip allows for removal of theobturator, while the camera/prism assembly is in place and overhangingthe lumen of the cannula. The obturator may simply be tilted away fromthe long axis of the cannula to clear the camera and prism. If theproximal surface of the tip is not tapered, the camera assembly may beremoved momentarily to clear the cylindrical space over the lumen toallow removal of the obturator.

As shown in FIG. 13, a surgeon inserts the cannula 4 with an obturator33 into the patient's brain until the distal end 6 d of the cannula issufficiently close to tissue 2 for surgery. While inserting the cannulaand obturator, the surgeon operates the camera and control system todisplay an image of the cannula lumen and structures at the distal endof the cannula on a display. Image data from camera 5 is transmitted tothe display 50 to provide an image or images 51 of the structures at thedistal end of the cannula through lumen 8 and the proximal surface ofthe obturator tip. The display may be operated by a control system whichis operable to receive image data from the camera, transmit the imagedata to the display, and also add additional images to the display suchas markers, cursors, and indicia of patient data. If the cannula lumenis large, the surgeon may directly view the proximal surface of theobturator tip to view the brain or blood proximate the distal surface ofthe obturator tip. 52

FIGS. 15, 16 and 17 depict exemplary images obtained by the camera whileadvancing the system through the brain. These are exemplary depictionsof what a surgeon would see while pushing the distal tip of theobturator, while disposed within the cannula with the distal surface ofthe obturator extending distally from the distal edge of the cannula,through the brain and toward a blood mass. These images correspond to aninsertion toward a blood mass that is somewhat deep in the brain, belowa layer of healthy brain tissue. Upon initial insertion into the brain,while the tip is passing through healthy brain tissue, the surgeon willsee an “image” of the healthy brain tissue, which appears white oroff-white (various shades of ivory, bone, linen, etc.). Each imageincludes an image of the obturator shaft 35 and the obturator tipproximal surface 34 p, and a portion of the cannula wall surface 53. Theimage will appear as a ring 54 or partial ring, around an outerperipheral portion of the tip proximal surface. A marker 55,corresponding to an index on the cannula or obturator or a predeterminedposition relative to the camera, with or without an index, may beinserted into the display by the operating software, to inform thesurgeon of the relationship of the displayed image to the position ofthe cannula and obturator. The index may, for example, be thecircumferential position of camera, and the marker can be imposed on thedisplay in a position opposite the camera (this is the configurationshown), though the marker can be imposed on the display in anypredetermined relationship to the index. The index can be any feature ofcannula or obturator. These features are depicted in FIGS. 15, 16 and17. Additional features visible in these views include a bright ring 56inside the image ring 54, and an epoxy ring 57 used to secure theobturator shaft to the obturator tip.

Upon initial insertion, as the tip enters healthy brain tissue overlyingthe blood mass, the ring 54 will appear white, and the surgeon will seean “image” of the brain tissue, which appears white (brain colored). Asthe tip enters the blood mass, the ring 54 will turn red, and thesurgeon will see an “image” of the blood mass, which appears as bloodred or black. This is depicted in FIG. 16. If the tip is located at themargin of the blood mass, the “image” will include a circumferentialportion that is white (brain colored) and a circumferential portion thatis red or black (blood-colored), and various shades of both, dependingon thickness of any blood between the tip and the brain tissue (forexample, for circumferential regions of the distal surface of the tipnear the margins of the blood mass, the corresponding image transmittedthrough the proximal surface of the tip will be pinkish, or a mix of theblood and brain shades. The surgeon can determine the distal margin(relative to the cannula and entry point in the skull) of the blood massby pushing the tip further into the brain, after entry into the bloodmass (as indicated by an image similar to FIG. 16) until an image ofbrain tissue again appears from the proximal surface of the tip (asindicated by an image similar to FIG. 15). The surgeon can determine thelateral extent of the blood mass (that it, its width along an axisperpendicular to the long axis of the cannula) by tilting the assembledcannula and obturator, to move the tip laterally until an image of braintissue is visible on one side of the ring 54. This is depicted in FIG.17. The image will be reversed by the tip as constructed as shown inFIGS. 12 and 13, but may be reversed by the display system, or it may bereversed by a reversing prism or a reversing/inverting prism provided asprism/reflector 12. As shown FIG. 17, a fiducial marker 58 or otherindicia may be imposed on the proximal or distal face of the obturatortip. This fiducial marker may be used by the surgeon to determine theangular orientation of the obturator relative to the camera viewingaxis, and/or confirm that the image is displayed without reversal (sothat the displayed image is actually a reversed image of underlyingtissue, as a result of the lensing effect of the obturator tip) ordisplayed with reversal (so that the image is a proper image obtainedafter the image has been reversed by the control system, after havingbeen reversed as a result of the lensing effect of the obturator tip) sothat it corresponds to the underlying tissue structure. The controlsystem can be programmed such that it is operable to determine thepresence or absence of the fiducial marker in the detected image of theproximal surface of the obturator tip, and, upon detection of thefiducial marker, generate a presented image which is reversed vis-à-visthe detected image, and present the presented image on the display, or,upon determining that no fiducial marker appears in the detected image,generate a presented image which is not reversed vis-à-vis the detectedimage. When the proximal surface image is reversed by the controlsystem, the fiducial marker in a reverse image along with the reverseimage of the proximal surface will be displayed, to indicate to thesurgeon that the image displayed has been reversed, and is orientedrelative to the camera viewing axis so that left, right, up and down onthe display corresponds to left, right, up and down relative to thecannula. In the illustrated example, the fiducial marker is the letterB, which is asymmetric, so that reversal is obvious. The fiducial markermay take any form recognizable by the control system, such as a barcode,or a distinctive array of dots, and is preferably asymmetric. Thefiducial marker may also be used by the control system, if, inconjunction with the obturator mount, the fiducial marker is placed inpredetermined relationship with the camera, to determine the orientationof the captured image and rotate the displayed image so that thedisplayed image corresponds structural features of the cannula system,and thus assist the surgeon in properly interpreting the displayedimage.

The obturator tip may be configured to avoid image reversal, byproviding, with the obturator tip, several longitudinally extendingoptically opaque structures within the otherwise optically transmissivetip, or by providing several optically transmissive longitudinallyextending structures within an otherwise optically opaque tip, tocomprise an overall optically transmissive tip through which light fromthe distal surface is transmitted through the optically transmissivestructures (and thus avoids reversal of the single piece structure ofFIGS. 1 through 3). This is illustrated in FIG. 18, which shows theobturator tip 34 with a plurality of light transmissive elements 59extending longitudinally from the distal face 34 d, along thecircumferential surface 34 c, to the proximal face 34 p of the obturatortip. These elements may be separated by longitudinally opaque elements60 extending longitudinally from the distal face 34 d to the proximalface 34 p of the obturator tip, or they may be discrete elementsdisposed immediately abutting adjacent discrete opaque elements, suchthat each light transmissive element transmits light from the distalface to the proximal face without reversal of the overall image. Thelight transmissive elements may extend to the outer surface of thecircumferential surface, as shown, or they may be embedded below thecircumferential surface. FIG. 19 illustrates another non-reversingconfiguration of the obturator tip 34. This obturator tip includes theconically convex distal surface 34 d, an axially short circumferentialsurface 34 c, without the conically convex proximal surface 34 p shownin FIG. 13, and includes an annular groove 61, in the proximal surface,extending from the proximal extent of the obturator tip toward thedistal surface, between a circumferential wall portion 34 w, in thelongitudinal region of the circumferential surface and the socket orhosel 62, extending from the distal portion of the tip, with bore 63into which the obturator shaft (item 35 of FIG. 13) is inserted.

For any of the embodiments disclosed herein, the tubular body may beprovided with at least about 4 light sources, and in someimplementations at least about 10 or 15 or 20 or 30 or more lightsources such as LED's. In one implementation at least about 35 or 40LED's are carried on the tubular body and exposed to the central lumen.Some or all of the LED's can be right angle LED's.

The light sources may be positioned within about 50% or 30% or 20% or10% or less of the length of the tubular body from the distal end. Insome implementations, the light sources are positioned within about 5 cmor about 3 cm or about 1 or 2 cm from the distal end. The plurality oflight sources may reside on a common transverse plane, or a ring oflight sources may reside substantially on a common transverse plane(meaning the light sources in that ring may have a small axial positionvariation but are within about +/−1 cm or 0.5 cm or less of a transverseplane).

The tubular body may be provided with a first, distal ring of lightsources positioned distally of a second, proximal ring of light sources.At least a third, intermediate ring of light sources may be positionedin between the first and second rings. The rings may be separated by atleast about 2 cm and in some implementations at least about 3 cm or 4 cmor more.

If only a single light source or ring of light sources is provided atthe distal end of the tubular body, the light source may becomeobstructed if blood enters the lumen at the distal end of the tubularbody. Providing at least one and preferably two or more secondary lightsources spaced axially apart proximally along the length of the lumenallows continuity of light in the event that one or more distal lightsources becomes obstructed.

The systems can be configured as a thermally stable system for accessingand imaging an intracranial hemorrhage. When so configured, the devicemay comprise an elongate tubular body, having a proximal end, a distalend, and a lumen; a plurality of LED light sources carried by thetubular body within about the distal most 30% or 20% or 10% of thelength of the tubular body; and a sensor/camera mounted at the proximalend of the tubular body. The lumen accommodates simultaneous viewing ofthe ICH site while performing procedures on the ICH. Operation of theLED light sources in ambient air at STP for at least 60 minutes at anintensity of at least about 3,000 lumens elevates the distal end of thetubular body by no more than about 22° C. or 17° C. or 10° C. (40° F. or30° F. or 20° F.). Preferably, operation of the LED's within the rangeof from about 3500 to about 4500 lumens elevates the distal end of thetubular body by no more than about 22° C. or 17° C. or 10° C. (40° F. or30° F. or 20° F.). Operation of the device in vivo for aninter-operative time frame needed to treat an ICH (typically 30 to 60minutes) will preferably elevate tissue in contact with the distal endto a temperature of no more than about 45° C., optimally no more thanabout 43 or 40° C.

The access and imaging device may comprise at least 3 LEDs andoptionally at least about 10 or 20 or 30 LED's within the most distal30% of the length of the tubular body. The LED's may be positioned inthe same transverse plane, or at least one and preferably a plurality ofLED's in each of a first and second and optionally third or fourthtransverse planes spaced axially apart along the length of the tubularbody. At least one and preferably a plurality of the LED's are rightangle LED's. At least one LED operates at a wavelength of from about 300nm to about 1 mm, preferably within the range of from about 390 nm toabout 700 nm. A first set of LED's may operate at a first wavelength inthe visible range, and a second set of LED's may operate at a second,different wavelength, such as in the infrared range. Alternatively, atleast one and preferably a plurality of LED's are tunable between thefirst and second wavelengths.

The access and imaging device may additionally comprise an opticalelement carried by the proximal end and positioned within an opticalpath between the sensor and the distal end. The optical element maycomprise a prism, a mirror or other reflector, having a distally facingsurface. The central lumen may have a longitudinal axis extendingconcentrically therethrough; the imaging sensor has a primary viewingaxis; and the longitudinal axis and the primary viewing axis intersectat the optical element at an angle. The angle is greater than zerodegrees and in some implementations may be within the range of fromabout 70° and 110°, or within the range of from about 85° and 95°. Theprism bends light rays propagating proximally through the tubular bodyand directs them laterally to the sensor.

The distal surface of the prism overhangs the central lumen by no morethan about 25% of the inside diameter of the lumen, preferably no morethan about 15% or 10% of the inside diameter of the lumen. The prism maybe rigidly mounted or adjustably mounted with respect to the tubularbody. A prism viewing axis (the secondary viewing axis) extends at aperpendicular to the distal optical surface of the prism, and the prismviewing axis is non-parallel to the central longitudinal axis of thetubular body. The prism viewing axis may intersect the centrallongitudinal axis at a point spaced apart from the proximal end by adistance within the range of from about 80% and 120% of the length ofthe tubular body and preferably at a point spaced apart from theproximal end by a distance within the range of from about 95% and 105%of the length of the tubular body.

The sensor may capture images in either or both the visible and at leastone non-visible wavelength, such as infrared. Alternatively, a firstsensor with sensitivity in the visible and a second sensor withsensitivity in the infrared may be provided. A beam splitter may beprovided to direct reflected light to each of the two sensors. Thesensor may be provided with control circuitry, for providing control ofdigital zoom, contrast, brightness, saturation, sharpness, whitebalance, and horizontal and vertical alignment and rotation.

The systems can be configured as self-contained medical visualizationand access devices. When so configured, the device may comprise anelongate tubular body, having a proximal end, a distal end, and aworking channel extending therethrough; and a sensor carried by theproximal end and configured to capture image data propagated in freespace through the working channel, where the relationship between thesensor and the working channel is fixed, and manipulation of surgicaltools and visualization may be simultaneously accomplished through theworking channel. That is, the surgeon can insert a tool, such as aaspirator or macerator, without having to remove the camera to make wayfor the tools, and continue viewing a display of an image obtained bythe camera while manipulating the tool tips within the surgical field ator beyond the distal end of the cannula. The device may further comprisean optical element such as a prism, mirror or other reflector fordirecting image data from the working channel laterally to the sensor. Asecondary viewing axis (from the prism distal face to the distal end ofthe cannula) extending distally from the prism through free space in theworking channel intersects a central longitudinal axis of the workingchannel at a point that is at least about 75% of the length of thetubular body from the proximal end. A self-contained medicalvisualization and access device may also further comprise a plurality ofLED's within the working channel as described previously.

Any of the foregoing devices may additionally be provided with glarereduction optimization. For example, the central lumen may be providedwith a plurality of optical baffles in between a distal light source andthe proximal end to inhibit glare from reflected light from the lightsource in a proximal direction. At least 3 and preferably more lightsources are carried by the interior wall of the tubular body, positionedwithin about 50% and preferably within about 20% of the length of thetubular body from the distal end. The optical baffles may comprise apolarizing grating, which may be carried by the light source and/orcarried adjacent the sensor. Alternatively, the optical baffles maycomprise a mechanical surface structure on the interior wall such as aplurality of axially spaced apart ridges or grooves or a surface texturewhich dissipates reflection. The mechanical surface structure maycomprise a helical ridge or channel, or discrete circular ringssurrounding the central lumen and spaced axially apart. A helical ridgemay be formed integrally with the tubular body, or by introducing ahelical structure such as a spring into the central lumen.

Any of the foregoing may be provided with a focus and/or depth of fieldadjustability by moving optical components along an axis other than thecentral longitudinal axis, thereby optimizing access to the centrallumen for use of the obturator or surgical tools and preserving directline of sight viewing through the central lumen.

For example, the intracranial hemorrhage visualization and access devicemay comprise an elongate tubular body, having a proximal end, a distalend, and a central lumen. A sensor may be carried by the proximal end,configured to capture focused images of tissue beyond the distal end ofthe tubular body and within a depth of field. Movement of an opticalelement radially inwardly or outwardly with respect to the longitudinalaxis of the tubular body changes a focal length captured by the sensor.The optical element may be the sensor, or may be a lens.

A prism may be carried by the proximal end and configured to direct animage propagated through free space through the central lumen to thesensor. An optical aperture may be provided in a light path between theprism and the sensor. In some implementations, the aperture has adiameter within the range of from about 1.3 mm to about 1.7 mm. Theprism may be immovably secured to the tubular body. The optical systemmay additionally comprise a lens in the optical path and an adjustmentcontrol such as a knob for optical magnification of the target tissue.

Any of the optical elements disclosed herein, at the proximal end of thefree space light path extending through the central lumen (e.g., aprism) may have a planar distal optical surface, and a secondary viewingaxis extending through the central lumen at a perpendicular to thedistal optical surface. The tubular body may be characterized by acentral longitudinal axis, and the secondary viewing axis intersects thecentral longitudinal axis near the distal end of the tubular body, at apoint spaced apart from the proximal end by a distance within the rangeof from about 80% to about 120% of the length of the tubular body; insome implementations within the range of from about 95% to about 105% ofthe length of the tubular body.

The prism may bend light to an angle within the range of from about 70°to about 110° from the secondary viewing axis (the prism viewing axis)toward the primary viewing axis, and, in some implementations within therange of from about 85° to about 95° from the prism viewing axis. Theprism may overhang the central lumen by no more than about 25% of theinside diameter of the central lumen, and preferably no more than about15% of the inside diameter of the central lumen. The prism may bendlight to an angle within the range of from about 70° to about 110° fromthe secondary viewing axis, and, in some implementations within therange of from about 85° to about 95° from the secondary viewing axis.The prism may overhang the central lumen by no more than about 25% ofthe inside diameter of the central lumen, and preferably no more thanabout 15% of the inside diameter of the central lumen.

A feature of the devices described in reference to FIGS. 1 through 9 isthe obstruction resistant optical path. Should the system include adistally located optical element (such as a window or lens positioned ator near the distal end of the sheath), the image can become obstructedby blood or other tissue coming into contact with the distal opticalsurface. This necessitates removal of the device to clear the surface.By positioning the distal most optical surface at the proximal end ofthe sheath, the optical surface is spaced well apart from the surgicalfield and the risk of blood or debris contacting the optical surface isminimized. Thus, an enhanced optical performance visualization systemfor an access device may comprise an elongate tubular body, having aproximal end, a distal end, and a central lumen extending axiallytherethrough, without an optical element immovably fixed at the distalend of the elongate tubular body (though allowing for the removableobturator shown in FIGS. 12 through 19). An optical system may beprovided, comprising a sensor, a lens and a distal most optical surfacefacing in a distal direction to capture images beyond the distal end ofthe sheath. The optical surface is spaced apart from the distal end byat least about 80% or 90% of the length of the tubular body such that itis out of range of splashes or debris disrupted by a surgical procedureconducted through the central lumen. In different implementations, theoptical surface may be positioned at least about 50 mm and in someembodiments at least about 75 mm or 100 mm or 120 mm or more proximallyfrom the distal end of the sheath.

A feature of the devices described in reference to FIGS. 12 through 19include the obturator, which is configured for off-axis introductioninto the proximal end of the sheath, and the optically translucentdistal tip. The obturator may comprise an elongate support and anobturator tip at the distal end of the support. The obturator tip mayhave a proximal surface which has a tapered surface which tapersradially inwardly in the proximal direction. The proximal surface may beradially symmetric, such as in the shape of a cone. A cylindricalsection may extend distally from a distal end of the proximal surface,dimensioned for sliding close fit within the sheath. A distal surfacemay comprise a conical distal section in which the diameter tapersradially inwardly in the distal direction. Preferably the body is atleast translucent and optionally transparent to light such as light inthe visible range, though the advantage of off-axis insertion of theobturator may be obtained with an opaque obturator tip, as in FIG. 11.The support may be tubular and may contain electrical or opticalconductors such as to operate an infra-red mapping sensor carried by theobturator body preferably at the distal end. The distal conical surfaceis helpful in advancing through soft tissue, while the proximal conicalsurface facilitates removal of the obturator without the need todisplace the prism or other optical element overhanging the centrallumen at the proximal end of the sheath.

Thus an intracranial hemorrhage visualization and access system maycomprise an elongate tubular body, having a proximal end, a distal end,a central lumen and a longitudinal axis extending therethrough. A sensorcarried by the proximal end is configured to capture image data throughthe central lumen, the sensor having a primary viewing axis. An opticalelement carried by the proximal end overhangs and extends into the pathof a proximal extension of the central lumen. An obturator is axiallyadvanceable through the central lumen. The overhanging optical elementinterferes with introduction of the obturator into the proximal end ofthe sheath along the central longitudinal axis of the sheath, but theobturator is configured to enter the proximal end of the sheath along anentry axis that resides at an angle to the central longitudinal axis andthen the support may be rotated into parallel or concentric with thecentral longitudinal axis of the sheath and the obturator may thereafterbe advanced axially through the lumen to the distal end coaxially withthe tubular body. The axial length of the cylindrical section is lessthan the distance from the proximal end of the central lumen to theoptical element. Thus, the portion of the camera portion of the cameraoverhanging the lumen is spaced proximally from the proximal end of thecannula to accommodate passage of the obturator tip, and the obturatortip is configured to pass into the cannula lumen while the portion ofthe camera overhanging the lumen is in place overhanging the lumen.

The obturator tip is preferably sufficiently optically transmissive thatcolor changes beyond the distal surface can be identified by directvisualization of the proximal surface. This enables the clinician to seewhen the distal surface is in contact with brain tissue, clot orcerebrospinal fluid. In one implementation, the obturator isadditionally provided with a sensor such as an IR sensor.

While the preferred embodiments of the devices and methods have beendescribed in reference to the environment in which they were developed,they are merely illustrative of the principles of the inventions. Thedevices may be used various intracerebral procedures such asintra-ventricular hemorrhage procedures, neuro-stimulation procedures,and tumor resection. The elements of the various embodiments may beincorporated into each of the other species to obtain the benefits ofthose elements in combination with such other species, and the variousbeneficial features may be employed in embodiments alone or incombination with each other. Other embodiments and configurations may bedevised without departing from the spirit of the inventions and thescope of the appended claims.

We claim:
 1. A cannula system for accessing a surgical field, saidcannula system comprising: a cannula comprising a cannula tube with aproximal end and a distal end and a lumen extending from the proximalend to the distal end; and a camera assembly secured to the proximal endof the cannula, with a portion of the camera assembly overhanging thelumen and extending into a cylindrical space defined by the lumen of thecannula tube; wherein the camera assembly has a distal-most opticalsurface, and said distal-most optical surface is disposed proximate theproximal end of the cannula tube; wherein the camera assembly has aviewing axis, and the distal-most optical surface of the camera systemis disposed over the proximal end of the cannula tube and angled to aimthe viewing axis to intersect with a central longitudinal axis of thecannula tube at the distal end of the cannula tube.
 2. The cannulasystem of claim 1, wherein: the camera assembly comprises an imagingsensor and a lens and a prism, and the prism is the portion of thecamera overhanging the lumen, and the distal-most optical surface of thecamera system is a distal surface of the prism.
 3. The cannula system ofclaim 2, wherein the prism overhangs the lumen by no more than about 25%of the inside diameter of the lumen.
 4. The cannula system of claim 1,wherein the distal-most optical surface overhangs the lumen by no morethan about 25% of the inside diameter of the lumen.
 5. A cannula systemfor accessing a surgical field, said cannula system comprising: acannula comprising a cannula tube with a proximal end and a distal endand a lumen extending from the proximal end to the distal end; and acamera assembly secured to the proximal end of the cannula, with aportion of the camera assembly overhanging the lumen and extending intoa cylindrical space defined by the lumen of the cannula tube; whereinthe camera assembly has a distal-most optical surface, and saiddistal-most optical surface is disposed proximate the proximal end ofthe cannula tube; wherein the portion of the camera assembly overhangingthe lumen extends into the lumen of the cannula tube.
 6. The cannulasystem of claim 5, wherein the distal-most optical surface overhangs thelumen by no more than about 25% of the inside diameter of the lumen. 7.A cannula system for accessing a surgical field, said cannula systemcomprising: a cannula comprising a cannula tube with a proximal end anda distal end and a lumen extending from the proximal end to the distalend; and a camera assembly secured to the proximal end of the cannula,with a portion of the camera assembly overhanging the lumen andextending into a cylindrical space defined by the lumen of the cannulatube; wherein the camera assembly has a distal-most optical surface, andsaid distal-most optical surface is disposed proximate the proximal endof the cannula tube; wherein the camera assembly comprises an imagingsensor and a lens and a prism, and the prism is the portion of thecamera overhanging the lumen.
 8. The cannula system of claim 7 whereinthe distal-most optical surface is a distally facing surface of theprism and the prism is characterized by a viewing axis which extendsthrough the lumen, and wherein an imaging sensor viewing axis issubstantially perpendicular to the prism viewing axis.
 9. The cannulasystem of claim 8, wherein the prism viewing axis extends through thelumen at a perpendicular to the distally facing surface of the prism.10. The cannula system of claim 8, wherein the prism viewing axisintersects a central long axis of the cannula at a point spaced apartfrom the proximal end of the cannula by a distance within the range ofabout 80% to 120% of the length of the cannula tube.
 11. The cannulasystem of claim 8, wherein the prism viewing axis intersects a long axisof the cannula at a point spaced apart from the proximal end of thecannula by a distance within the range of about 95% to 105% of thelength of the cannula tube.
 12. The cannula system of claim 7, whereinthe prism overhangs the lumen by no more than about 25% of the insidediameter of the lumen.
 13. A cannula system for accessing a surgicalfield, said cannula system comprising: a cannula comprising a cannulatube with a proximal end and a distal end and a lumen extending from theproximal end to the distal end; and a camera assembly secured to theproximal end of the cannula, with a portion of the camera assemblyoverhanging the lumen and extending into a cylindrical space defined bythe lumen of the cannula tube; wherein the camera assembly has adistal-most optical surface, and said distal-most optical surface isdisposed proximate the proximal end of the cannula tube; wherein thedistal-most optical surface of the camera system is spaced proximallyfrom the proximal end of the cannula tube; and the camera assemblycomprises an imaging sensor and a lens and a prism, and the prism is theportion of the camera overhanging the lumen, and the distal-most opticalsurface of the camera system is a distal surface of the prism.
 14. Thecannula system of claim 13, wherein the prism overhangs the lumen by nomore than about 25% of the inside diameter of the lumen.
 15. A cannulasystem for accessing a surgical field, said cannula system comprising: acannula comprising a cannula tube with a proximal end and a distal endand a lumen extending from the proximal end to the distal end; and acamera assembly secured to the proximal end of the cannula, with aportion of the camera assembly overhanging the lumen and extending intoa cylindrical space defined by the lumen of the cannula tube; whereinthe camera assembly has a distal-most optical surface, and saiddistal-most optical surface is disposed proximate the proximal end ofthe cannula tube; wherein the distal-most optical surface of the camerasystem is disposed over the proximal end of the cannula tube; and thecamera assembly comprises an imaging sensor and a lens and a prism, andthe prism is the portion of the camera overhanging the lumen, and thedistal-most optical surface of the camera system is a distal surface ofthe prism.
 16. The cannula system of claim 15, wherein the prismoverhangs the lumen by no more than about 25% of the inside diameter ofthe lumen.
 17. A cannula system for accessing a surgical field, saidcannula system comprising: a cannula comprising a cannula tube with aproximal end and a distal end and a lumen extending from the proximalend to the distal end; and a camera assembly secured to the proximal endof the cannula, with a portion of the camera assembly overhanging thelumen and extending into a cylindrical space defined by the lumen of thecannula tube; wherein the camera assembly has a distal-most opticalsurface, and said distal-most optical surface is disposed proximate theproximal end of the cannula tube; wherein the portion of the cameraassembly that overhangs the lumen overhangs the lumen by no more thanabout 25% of the inside diameter of the lumen.